1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle driven by an engine and a motor. In particular the invention relates to a control apparatus for a hybrid vehicle, which enables appropriate energy management of a high voltage power storage unit for driving a motor depending on 12V electric power consumption.
This application is based on Japanese Patent Application No. Hei 11-286111 (Unpublished), the contents of which are incorporated herein by reference.
2. Description of the Related Art
Heretofore there is known a hybrid vehicle incorporating a motor in addition to an engine as a drive source for driving vehicle.
For one type of such hybrid vehicle, there is a parallel hybrid vehicle where the motor is used as an auxiliary drive source for assisting the output from the engine. With this parallel hybrid vehicle, for example at the time of acceleration, the engine is drive assisted by means of the motor, while at the time of deceleration, various control is carried out such as performing charging of a battery by deceleration regeneration, so that the electrical energy (hereinafter remaining charge) of the battery can be maintained to satisfy the requirements of the driver (for example, as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 7-123509.)
The battery of the high voltage system that is generally installed in the abovementioned conventional parallel hybrid vehicle, supplies electric power to a motor that is mainly an auxiliary drive to the engine, and stores the regenerative electric power supplied from the motor at the time of deceleration regeneration. However, there is a case where, for example, the remaining charge of this high voltage system battery is affected by electric power consumption of the 12V system, such as for engine accessories, headlamps and an air conditioner.
For example, when electric power consumption of the 12V system increases, a portion of the electric power that is supposed to be supplied to the high voltage system battery by deceleration regeneration, is directed to the electric power consumption of the 12V system, and electric power to be supplied to the battery of the high voltage system is decreased. Furthermore, there is a case where, when drive assistance is performed from the high voltage system battery to accelerate, if a portion is supplied to electric power consumption of the 12V system, the remaining charge is decreased by that portion.
To deal with these, it is possible to solve the abovementioned problems by enhancing this high voltage system battery so as to avoid detriment to the high voltage system battery, or to increase the capacity of the 12V system battery to provide a margin for energy management of the electric power consumption of the 12V system. However, there is a problem in that the weight of the high voltage battery or the 12V system battery is increased, which increases the vehicle weight.
Therefore, this invention provides a control apparatus for a hybrid vehicle which increases electric power for supplying the power storage unit, and also suppresses the discharge amount from the power storage unit, depending on the low voltage system power consumption.
With the first aspect of the present invention, a control apparatus for a hybrid vehicle which is provided with: an engine (for example, an engine E in an embodiment) for outputting a, driving force for a vehicle, a motor (a motor M) for assisting the output from the engine, a high voltage power storage unit (a battery 3) for supplying electric power to the motor, a voltage converter (a downverter 5) for lowering the voltage of the high voltage power storage unit to enable supply of electric power to a low voltage system such as a low voltage power storage unit (an auxiliary battery 4) and engine accessories, comprising: an electric power computing device (FIECU 11) for computing the electric power consumption of the low voltage system; and a storage amount controller for preventing the decrease of the storage amount of the high voltage power storage unit depending on the electric power consumption of the low voltage system.
With the second aspect of the present invention, the hybrid vehicle is further provided with a regeneration controller (a motor ECU 1) for setting a regeneration amount by the motor at the time of vehicle deceleration, to perform regeneration by the motor on the basis of the regeneration amount; and the storage amount controller is further provided with a vehicle speed detector (a vehicle speed sensor S1), an engine speed detector (an engine speed sensor S2) for detecting the engine speed of the engine, and a regeneration amount increasing device (step S407) for, when the vehicle speed (a control vehicle speed VP) detected by the vehicle speed detector is within a predetermined range (within the range set in step S404 and step S405), and the engine speed detected by the engine speed detector is greater than a predetermined speed (a predetermined value #NPRGELL), increasing the regeneration amount set by the regeneration controller, depending on the electric power consumption of the low voltage system.
With the third aspect of the present invention, the hybrid vehicle is further provided with an output assistance determining device (steps S122, S135) for determining, on the basis of a determination threshold value (an air intake passage pressure assistance trigger threshold value MAST, a throttle assistance trigger threshold value MTHAST, an air intake passage pressure assistance trigger threshold value MASTTH), approval or denial of output assistance of the engine by the motor, depending on the driving conditions of the vehicle, an output assistance controller (a motor ECU 1) for, when the output assistance determining device determines that output assistance of the engine by the motor is performed, setting the control amount of the motor to perform output assistance of the engine by the motor, and a generation controller (a motor ECU 1) for, when the output assistance determining device determines that output assistance of the engine by the motor is not performed, setting the generation amount by the motor to perform generation by the motor; and the storage amount controller is further provided with a generation amount increasing device (step S319) for increasing the generation amount set by the generation controller, depending on the electric power consumption of the low voltage system.
With the fourth aspect of the present invention, the hybrid vehicle is further provided with an output assistance determining device (steps S122, S135) for determining, on the basis of a determination threshold value (an air intake passage pressure assistance trigger threshold value MAST, a throttle assistance trigger threshold value MTHAST, an air intake passage pressure assistance trigger threshold value MASTTH), approval or denial of output assistance of the engine by the motor, depending on the driving conditions of the vehicle, and an output assistance controller (a motor ECU 1) for, when the output assistance determining device determines that output assistance of the engine by the motor is performed, setting the control amount of the motor to perform output assistance of the engine by the motor; and the storage amount controller is further provided with a high electric power consumption determining device (step S165) for determining whether a situation in which the electric power consumption of the low voltage system exceeding a predetermined value (a predetermined value #VELMAH) has continued for a certain duration (a predetermined value #TMELMA), and a determination threshold value correcting device (steps S158, S169, S198) for, when it is determined by the high electric power consumption determining device that a situation in which the electric power consumption of the low voltage system exceeding a predetermined value has continued for a certain duration, raising the determination threshold value which is the basis of approval or denial of output assistance by the output assistance determining device, depending on the electric powers consumption of the low voltage system.
With such constructions, depending on the electric power consumption of the low voltage system, the regeneration amount increasing device increases, for example, the regenerative electric power at the time of deceleration regeneration, so that it is possible to avoid a decrease of the supply amount of regenerative electric power to the high voltage power storage unit. Furthermore, depending on the electric power consumption of the low voltage system, the generation amount increasing device increases, for example the generation amount at the time of cruise, so that it is possible to increase the storage amount of the high voltage power storage unit in advance. Moreover, when the current consumption of the low voltage system is increased to greater than a predetermined value by the high electric power consumption determining device, by raising the determination threshold value of the output assistance for the engine from the motor output by means of the determination threshold value correcting device, for example, the frequency of the accelerating mode can be decreased and the frequency of cruise mode increased. Therefore, there is an effect in that the drop of the storage amount of the high voltage power storage unit due to the electric power consumption of the low voltage system is prevented, which enables appropriate energy management to be realized.
A fifth aspect of the invention is characterized in that the storage amount controller is further provided with a vehicle speed detector (a vehicle speed sensor S1), and the determination threshold value to be corrected by the determination threshold value correcting device is corrected depending on the vehicle speed (a control vehicle speed VP) detected by the vehicle speed detector (steps S157, S168, S197).
With such a construction, even when sufficient regenerative electric power cannot be maintained due to repeated starting and stopping at the time of low vehicle speed such as with traffic congestion, depending on the vehicle speed, for example, by raising the determination threshold value as the vehicle speed becomes lower, the frequency of acceleration mode can be further decreased and the frequency of cruise mode further increased. Consequently, there is an effect in that the drop of the storage amount of the high voltage power storage unit can be reliably prevented.
With the sixth aspect of the invention, by computing the low voltage system electric power consumption from the electric power downstream of the high voltage power storage unit and, upstream of the voltage converter, correction of the efficiency due to the temperature of the voltage converter is unnecessary. Therefore, there is an effect in that the low voltage system electric power consumption can be computed with high accuracy.
With the seventh aspect of the invention, by computing the low voltage system electric power consumption from the difference in the electric power between the upstream and downstream of the high voltage power storage unit, it is not necessary to specially install a detecting device upstream of the voltage converter. Therefore, there is an effect in that low cost can be expected.
With the eighth aspect of the invention, by computing the low voltage system electric power consumption from the ammeter (a current sensor S9) used in the fuel injection system, and the voltage of the low voltage power storage unit, the ammeter used in the fuel injection system is effectively utilized to enable high accuracy measurement. Therefore, there is an effect in that the accuracy of energy management can be improved.